The EH KT88 sounds neutral to me. I use them in triode mode. No tonality problems. Don't know the sound of NOS, it is probably richer, but EH KT88 does not make tonal funny stuff, it is forceful, and has clarity at least. Also they seem very stable with bias.

I did a check on my tester between a Shugang 88 and KT90....and lo behold the 88 didn't even get cherry red while the 90 had to be derated. The early Shugangs were appalling quality but the present Shugang quality has improved....---->haven't had'em in service for enough time to establish life. Despite the Shugang being lower priced --- > It's the glass envelope shape which isn't attractive on open amps.
I've lost track if Svetlana and /or reflecktor actually make all 88's and are then rebranded and farmed out with different vendors.

Originally posted by richwalters I did a check on my tester between a Shugang 88 and KT90....and lo behold the 88 didn't even get cherry red while the 90 had to be derated. The early Shugangs were appalling quality but the present Shugang quality has improved....---->haven't had'em in service for enough time to establish life. Despite the Shugang being lower priced --- > It's the glass envelope shape which isn't attractive on open amps.
I've lost track if Svetlana and /or reflecktor actually make all 88's and are then rebranded and farmed out with different vendors.

richj

If it was an Ei KT-90 from post-1999 or so, it likely had misaligned screens. Healthy KT-90s can take enormous dissipation loads.